The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_sem.c

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    1 /*-
    2  * Copyright (c) 2002 Alfred Perlstein <alfred@FreeBSD.org>
    3  * Copyright (c) 2003-2005 SPARTA, Inc.
    4  * Copyright (c) 2005 Robert N. M. Watson
    5  * All rights reserved.
    6  *
    7  * This software was developed for the FreeBSD Project in part by Network
    8  * Associates Laboratories, the Security Research Division of Network
    9  * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
   10  * as part of the DARPA CHATS research program.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/8.3/sys/kern/uipc_sem.c 217845 2011-01-25 20:54:15Z jhb $");
   36 
   37 #include "opt_compat.h"
   38 #include "opt_posix.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/condvar.h>
   42 #include <sys/fcntl.h>
   43 #include <sys/file.h>
   44 #include <sys/filedesc.h>
   45 #include <sys/fnv_hash.h>
   46 #include <sys/kernel.h>
   47 #include <sys/ksem.h>
   48 #include <sys/lock.h>
   49 #include <sys/malloc.h>
   50 #include <sys/module.h>
   51 #include <sys/mutex.h>
   52 #include <sys/priv.h>
   53 #include <sys/proc.h>
   54 #include <sys/posix4.h>
   55 #include <sys/semaphore.h>
   56 #include <sys/_semaphore.h>
   57 #include <sys/stat.h>
   58 #include <sys/syscall.h>
   59 #include <sys/syscallsubr.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/sysent.h>
   62 #include <sys/sysproto.h>
   63 #include <sys/systm.h>
   64 #include <sys/sx.h>
   65 #include <sys/vnode.h>
   66 
   67 #include <security/mac/mac_framework.h>
   68 
   69 /*
   70  * TODO
   71  *
   72  * - Resource limits?
   73  * - Update fstat(1)
   74  * - Replace global sem_lock with mtx_pool locks?
   75  * - Add a MAC check_create() hook for creating new named semaphores.
   76  */
   77 
   78 #ifndef SEM_MAX
   79 #define SEM_MAX 30
   80 #endif
   81 
   82 #ifdef SEM_DEBUG
   83 #define DP(x)   printf x
   84 #else
   85 #define DP(x)
   86 #endif
   87 
   88 struct ksem_mapping {
   89         char            *km_path;
   90         Fnv32_t         km_fnv;
   91         struct ksem     *km_ksem;
   92         LIST_ENTRY(ksem_mapping) km_link;
   93 };
   94 
   95 static MALLOC_DEFINE(M_KSEM, "ksem", "semaphore file descriptor");
   96 static LIST_HEAD(, ksem_mapping) *ksem_dictionary;
   97 static struct sx ksem_dict_lock;
   98 static struct mtx ksem_count_lock;
   99 static struct mtx sem_lock;
  100 static u_long ksem_hash;
  101 static int ksem_dead;
  102 
  103 #define KSEM_HASH(fnv)  (&ksem_dictionary[(fnv) & ksem_hash])
  104 
  105 static int nsems = 0;
  106 SYSCTL_DECL(_p1003_1b);
  107 SYSCTL_INT(_p1003_1b, OID_AUTO, nsems, CTLFLAG_RD, &nsems, 0,
  108     "Number of active kernel POSIX semaphores");
  109 
  110 static int      kern_sem_wait(struct thread *td, semid_t id, int tryflag,
  111                     struct timespec *abstime);
  112 static int      ksem_access(struct ksem *ks, struct ucred *ucred);
  113 static struct ksem *ksem_alloc(struct ucred *ucred, mode_t mode,
  114                     unsigned int value);
  115 static int      ksem_create(struct thread *td, const char *path,
  116                     semid_t *semidp, mode_t mode, unsigned int value,
  117                     int flags, int compat32);
  118 static void     ksem_drop(struct ksem *ks);
  119 static int      ksem_get(struct thread *td, semid_t id, struct file **fpp);
  120 static struct ksem *ksem_hold(struct ksem *ks);
  121 static void     ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks);
  122 static struct ksem *ksem_lookup(char *path, Fnv32_t fnv);
  123 static void     ksem_module_destroy(void);
  124 static int      ksem_module_init(void);
  125 static int      ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
  126 static int      sem_modload(struct module *module, int cmd, void *arg);
  127 
  128 static fo_rdwr_t        ksem_read;
  129 static fo_rdwr_t        ksem_write;
  130 static fo_truncate_t    ksem_truncate;
  131 static fo_ioctl_t       ksem_ioctl;
  132 static fo_poll_t        ksem_poll;
  133 static fo_kqfilter_t    ksem_kqfilter;
  134 static fo_stat_t        ksem_stat;
  135 static fo_close_t       ksem_closef;
  136 
  137 /* File descriptor operations. */
  138 static struct fileops ksem_ops = {
  139         .fo_read = ksem_read,
  140         .fo_write = ksem_write,
  141         .fo_truncate = ksem_truncate,
  142         .fo_ioctl = ksem_ioctl,
  143         .fo_poll = ksem_poll,
  144         .fo_kqfilter = ksem_kqfilter,
  145         .fo_stat = ksem_stat,
  146         .fo_close = ksem_closef,
  147         .fo_flags = DFLAG_PASSABLE
  148 };
  149 
  150 FEATURE(posix_sem, "POSIX semaphores");
  151 
  152 static int
  153 ksem_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
  154     int flags, struct thread *td)
  155 {
  156 
  157         return (EOPNOTSUPP);
  158 }
  159 
  160 static int
  161 ksem_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
  162     int flags, struct thread *td)
  163 {
  164 
  165         return (EOPNOTSUPP);
  166 }
  167 
  168 static int
  169 ksem_truncate(struct file *fp, off_t length, struct ucred *active_cred,
  170     struct thread *td)
  171 {
  172 
  173         return (EINVAL);
  174 }
  175 
  176 static int
  177 ksem_ioctl(struct file *fp, u_long com, void *data,
  178     struct ucred *active_cred, struct thread *td)
  179 {
  180 
  181         return (EOPNOTSUPP);
  182 }
  183 
  184 static int
  185 ksem_poll(struct file *fp, int events, struct ucred *active_cred,
  186     struct thread *td)
  187 {
  188 
  189         return (EOPNOTSUPP);
  190 }
  191 
  192 static int
  193 ksem_kqfilter(struct file *fp, struct knote *kn)
  194 {
  195 
  196         return (EOPNOTSUPP);
  197 }
  198 
  199 static int
  200 ksem_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
  201     struct thread *td)
  202 {
  203         struct ksem *ks;
  204 #ifdef MAC
  205         int error;
  206 #endif
  207 
  208         ks = fp->f_data;
  209 
  210 #ifdef MAC
  211         error = mac_posixsem_check_stat(active_cred, fp->f_cred, ks);
  212         if (error)
  213                 return (error);
  214 #endif
  215         
  216         /*
  217          * Attempt to return sanish values for fstat() on a semaphore
  218          * file descriptor.
  219          */
  220         bzero(sb, sizeof(*sb));
  221         sb->st_mode = S_IFREG | ks->ks_mode;            /* XXX */
  222 
  223         sb->st_atimespec = ks->ks_atime;
  224         sb->st_ctimespec = ks->ks_ctime;
  225         sb->st_mtimespec = ks->ks_mtime;
  226         sb->st_birthtimespec = ks->ks_birthtime;        
  227         sb->st_uid = ks->ks_uid;
  228         sb->st_gid = ks->ks_gid;
  229 
  230         return (0);
  231 }
  232 
  233 static int
  234 ksem_closef(struct file *fp, struct thread *td)
  235 {
  236         struct ksem *ks;
  237 
  238         ks = fp->f_data;
  239         fp->f_data = NULL;
  240         ksem_drop(ks);
  241 
  242         return (0);
  243 }
  244 
  245 /*
  246  * ksem object management including creation and reference counting
  247  * routines.
  248  */
  249 static struct ksem *
  250 ksem_alloc(struct ucred *ucred, mode_t mode, unsigned int value)
  251 {
  252         struct ksem *ks;
  253 
  254         mtx_lock(&ksem_count_lock);
  255         if (nsems == p31b_getcfg(CTL_P1003_1B_SEM_NSEMS_MAX) || ksem_dead) {
  256                 mtx_unlock(&ksem_count_lock);
  257                 return (NULL);
  258         }
  259         nsems++;
  260         mtx_unlock(&ksem_count_lock);
  261         ks = malloc(sizeof(*ks), M_KSEM, M_WAITOK | M_ZERO);
  262         ks->ks_uid = ucred->cr_uid;
  263         ks->ks_gid = ucred->cr_gid;
  264         ks->ks_mode = mode;
  265         ks->ks_value = value;
  266         cv_init(&ks->ks_cv, "ksem");
  267         vfs_timestamp(&ks->ks_birthtime);
  268         ks->ks_atime = ks->ks_mtime = ks->ks_ctime = ks->ks_birthtime;
  269         refcount_init(&ks->ks_ref, 1);
  270 #ifdef MAC
  271         mac_posixsem_init(ks);
  272         mac_posixsem_create(ucred, ks);
  273 #endif
  274 
  275         return (ks);
  276 }
  277 
  278 static struct ksem *
  279 ksem_hold(struct ksem *ks)
  280 {
  281 
  282         refcount_acquire(&ks->ks_ref);
  283         return (ks);
  284 }
  285 
  286 static void
  287 ksem_drop(struct ksem *ks)
  288 {
  289 
  290         if (refcount_release(&ks->ks_ref)) {
  291 #ifdef MAC
  292                 mac_posixsem_destroy(ks);
  293 #endif
  294                 cv_destroy(&ks->ks_cv);
  295                 free(ks, M_KSEM);
  296                 mtx_lock(&ksem_count_lock);
  297                 nsems--;
  298                 mtx_unlock(&ksem_count_lock);
  299         }
  300 }
  301 
  302 /*
  303  * Determine if the credentials have sufficient permissions for read
  304  * and write access.
  305  */
  306 static int
  307 ksem_access(struct ksem *ks, struct ucred *ucred)
  308 {
  309         int error;
  310 
  311         error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid,
  312             VREAD | VWRITE, ucred, NULL);
  313         if (error)
  314                 error = priv_check_cred(ucred, PRIV_SEM_WRITE, 0);
  315         return (error);
  316 }
  317 
  318 /*
  319  * Dictionary management.  We maintain an in-kernel dictionary to map
  320  * paths to semaphore objects.  We use the FNV hash on the path to
  321  * store the mappings in a hash table.
  322  */
  323 static struct ksem *
  324 ksem_lookup(char *path, Fnv32_t fnv)
  325 {
  326         struct ksem_mapping *map;
  327 
  328         LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
  329                 if (map->km_fnv != fnv)
  330                         continue;
  331                 if (strcmp(map->km_path, path) == 0)
  332                         return (map->km_ksem);
  333         }
  334 
  335         return (NULL);
  336 }
  337 
  338 static void
  339 ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks)
  340 {
  341         struct ksem_mapping *map;
  342 
  343         map = malloc(sizeof(struct ksem_mapping), M_KSEM, M_WAITOK);
  344         map->km_path = path;
  345         map->km_fnv = fnv;
  346         map->km_ksem = ksem_hold(ks);
  347         LIST_INSERT_HEAD(KSEM_HASH(fnv), map, km_link);
  348 }
  349 
  350 static int
  351 ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
  352 {
  353         struct ksem_mapping *map;
  354         int error;
  355 
  356         LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
  357                 if (map->km_fnv != fnv)
  358                         continue;
  359                 if (strcmp(map->km_path, path) == 0) {
  360 #ifdef MAC
  361                         error = mac_posixsem_check_unlink(ucred, map->km_ksem);
  362                         if (error)
  363                                 return (error);
  364 #endif
  365                         error = ksem_access(map->km_ksem, ucred);
  366                         if (error)
  367                                 return (error);
  368                         LIST_REMOVE(map, km_link);
  369                         ksem_drop(map->km_ksem);
  370                         free(map->km_path, M_KSEM);
  371                         free(map, M_KSEM);
  372                         return (0);
  373                 }
  374         }
  375 
  376         return (ENOENT);
  377 }
  378 
  379 static int
  380 ksem_create_copyout_semid(struct thread *td, semid_t *semidp, int fd,
  381     int compat32)
  382 {
  383         semid_t semid;
  384 #ifdef COMPAT_FREEBSD32
  385         int32_t semid32;
  386 #endif
  387         void *ptr;
  388         size_t ptrs;
  389 
  390 #ifdef COMPAT_FREEBSD32
  391         if (compat32) {
  392                 semid32 = fd;
  393                 ptr = &semid32;
  394                 ptrs = sizeof(semid32);
  395         } else {
  396 #endif
  397                 semid = fd;
  398                 ptr = &semid;
  399                 ptrs = sizeof(semid);
  400                 compat32 = 0; /* silence gcc */
  401 #ifdef COMPAT_FREEBSD32
  402         }
  403 #endif
  404 
  405         return (copyout(ptr, semidp, ptrs));
  406 }
  407 
  408 /* Other helper routines. */
  409 static int
  410 ksem_create(struct thread *td, const char *name, semid_t *semidp, mode_t mode,
  411     unsigned int value, int flags, int compat32)
  412 {
  413         struct filedesc *fdp;
  414         struct ksem *ks;
  415         struct file *fp;
  416         char *path;
  417         Fnv32_t fnv;
  418         int error, fd;
  419 
  420         if (value > SEM_VALUE_MAX)
  421                 return (EINVAL);
  422 
  423         fdp = td->td_proc->p_fd;
  424         mode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
  425         error = falloc(td, &fp, &fd);
  426         if (error) {
  427                 if (name == NULL)
  428                         error = ENOSPC;
  429                 return (error);
  430         }
  431 
  432         /*
  433          * Go ahead and copyout the file descriptor now.  This is a bit
  434          * premature, but it is a lot easier to handle errors as opposed
  435          * to later when we've possibly created a new semaphore, etc.
  436          */
  437         error = ksem_create_copyout_semid(td, semidp, fd, compat32);
  438         if (error) {
  439                 fdclose(fdp, fp, fd, td);
  440                 fdrop(fp, td);
  441                 return (error);
  442         }
  443 
  444         if (name == NULL) {
  445                 /* Create an anonymous semaphore. */
  446                 ks = ksem_alloc(td->td_ucred, mode, value);
  447                 if (ks == NULL)
  448                         error = ENOSPC;
  449                 else
  450                         ks->ks_flags |= KS_ANONYMOUS;
  451         } else {
  452                 path = malloc(MAXPATHLEN, M_KSEM, M_WAITOK);
  453                 error = copyinstr(name, path, MAXPATHLEN, NULL);
  454 
  455                 /* Require paths to start with a '/' character. */
  456                 if (error == 0 && path[0] != '/')
  457                         error = EINVAL;
  458                 if (error) {
  459                         fdclose(fdp, fp, fd, td);
  460                         fdrop(fp, td);
  461                         free(path, M_KSEM);
  462                         return (error);
  463                 }
  464 
  465                 fnv = fnv_32_str(path, FNV1_32_INIT);
  466                 sx_xlock(&ksem_dict_lock);
  467                 ks = ksem_lookup(path, fnv);
  468                 if (ks == NULL) {
  469                         /* Object does not exist, create it if requested. */
  470                         if (flags & O_CREAT) {
  471                                 ks = ksem_alloc(td->td_ucred, mode, value);
  472                                 if (ks == NULL)
  473                                         error = ENFILE;
  474                                 else {
  475                                         ksem_insert(path, fnv, ks);
  476                                         path = NULL;
  477                                 }
  478                         } else
  479                                 error = ENOENT;
  480                 } else {
  481                         /*
  482                          * Object already exists, obtain a new
  483                          * reference if requested and permitted.
  484                          */
  485                         if ((flags & (O_CREAT | O_EXCL)) ==
  486                             (O_CREAT | O_EXCL))
  487                                 error = EEXIST;
  488                         else {
  489 #ifdef MAC
  490                                 error = mac_posixsem_check_open(td->td_ucred,
  491                                     ks);
  492                                 if (error == 0)
  493 #endif
  494                                 error = ksem_access(ks, td->td_ucred);
  495                         }
  496                         if (error == 0)
  497                                 ksem_hold(ks);
  498 #ifdef INVARIANTS
  499                         else
  500                                 ks = NULL;
  501 #endif
  502                 }
  503                 sx_xunlock(&ksem_dict_lock);
  504                 if (path)
  505                         free(path, M_KSEM);
  506         }
  507 
  508         if (error) {
  509                 KASSERT(ks == NULL, ("ksem_create error with a ksem"));
  510                 fdclose(fdp, fp, fd, td);
  511                 fdrop(fp, td);
  512                 return (error);
  513         }
  514         KASSERT(ks != NULL, ("ksem_create w/o a ksem"));
  515 
  516         finit(fp, FREAD | FWRITE, DTYPE_SEM, ks, &ksem_ops);
  517 
  518         FILEDESC_XLOCK(fdp);
  519         if (fdp->fd_ofiles[fd] == fp)
  520                 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
  521         FILEDESC_XUNLOCK(fdp);
  522         fdrop(fp, td);
  523 
  524         return (0);
  525 }
  526 
  527 static int
  528 ksem_get(struct thread *td, semid_t id, struct file **fpp)
  529 {
  530         struct ksem *ks;
  531         struct file *fp;
  532         int error;
  533 
  534         error = fget(td, id, &fp);
  535         if (error)
  536                 return (EINVAL);
  537         if (fp->f_type != DTYPE_SEM) {
  538                 fdrop(fp, td);
  539                 return (EINVAL);
  540         }
  541         ks = fp->f_data;
  542         if (ks->ks_flags & KS_DEAD) {
  543                 fdrop(fp, td);
  544                 return (EINVAL);
  545         }
  546         *fpp = fp;
  547         return (0);
  548 }
  549 
  550 /* System calls. */
  551 #ifndef _SYS_SYSPROTO_H_
  552 struct ksem_init_args {
  553         unsigned int    value;
  554         semid_t         *idp;
  555 };
  556 #endif
  557 int
  558 ksem_init(struct thread *td, struct ksem_init_args *uap)
  559 {
  560 
  561         return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
  562             0, 0));
  563 }
  564 
  565 #ifndef _SYS_SYSPROTO_H_
  566 struct ksem_open_args {
  567         char            *name;
  568         int             oflag;
  569         mode_t          mode;
  570         unsigned int    value;
  571         semid_t         *idp;   
  572 };
  573 #endif
  574 int
  575 ksem_open(struct thread *td, struct ksem_open_args *uap)
  576 {
  577 
  578         DP((">>> ksem_open start, pid=%d\n", (int)td->td_proc->p_pid));
  579 
  580         if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
  581                 return (EINVAL);
  582         return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
  583             uap->oflag, 0));
  584 }
  585 
  586 #ifndef _SYS_SYSPROTO_H_
  587 struct ksem_unlink_args {
  588         char            *name;
  589 };
  590 #endif
  591 int
  592 ksem_unlink(struct thread *td, struct ksem_unlink_args *uap)
  593 {
  594         char *path;
  595         Fnv32_t fnv;
  596         int error;
  597 
  598         path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
  599         error = copyinstr(uap->name, path, MAXPATHLEN, NULL);
  600         if (error) {
  601                 free(path, M_TEMP);
  602                 return (error);
  603         }
  604 
  605         fnv = fnv_32_str(path, FNV1_32_INIT);
  606         sx_xlock(&ksem_dict_lock);
  607         error = ksem_remove(path, fnv, td->td_ucred);
  608         sx_xunlock(&ksem_dict_lock);
  609         free(path, M_TEMP);
  610 
  611         return (error);
  612 }
  613 
  614 #ifndef _SYS_SYSPROTO_H_
  615 struct ksem_close_args {
  616         semid_t         id;
  617 };
  618 #endif
  619 int
  620 ksem_close(struct thread *td, struct ksem_close_args *uap)
  621 {
  622         struct ksem *ks;
  623         struct file *fp;
  624         int error;
  625 
  626         error = ksem_get(td, uap->id, &fp);
  627         if (error)
  628                 return (error);
  629         ks = fp->f_data;
  630         if (ks->ks_flags & KS_ANONYMOUS) {
  631                 fdrop(fp, td);
  632                 return (EINVAL);
  633         }
  634         error = kern_close(td, uap->id);
  635         fdrop(fp, td);
  636         return (error);
  637 }
  638 
  639 #ifndef _SYS_SYSPROTO_H_
  640 struct ksem_post_args {
  641         semid_t id;
  642 };
  643 #endif
  644 int
  645 ksem_post(struct thread *td, struct ksem_post_args *uap)
  646 {
  647         struct file *fp;
  648         struct ksem *ks;
  649         int error;
  650 
  651         error = ksem_get(td, uap->id, &fp);
  652         if (error)
  653                 return (error);
  654         ks = fp->f_data;
  655 
  656         mtx_lock(&sem_lock);
  657 #ifdef MAC
  658         error = mac_posixsem_check_post(td->td_ucred, fp->f_cred, ks);
  659         if (error)
  660                 goto err;
  661 #endif
  662         if (ks->ks_value == SEM_VALUE_MAX) {
  663                 error = EOVERFLOW;
  664                 goto err;
  665         }
  666         ++ks->ks_value;
  667         if (ks->ks_waiters > 0)
  668                 cv_signal(&ks->ks_cv);
  669         error = 0;
  670         vfs_timestamp(&ks->ks_ctime);
  671 err:
  672         mtx_unlock(&sem_lock);
  673         fdrop(fp, td);
  674         return (error);
  675 }
  676 
  677 #ifndef _SYS_SYSPROTO_H_
  678 struct ksem_wait_args {
  679         semid_t         id;
  680 };
  681 #endif
  682 int
  683 ksem_wait(struct thread *td, struct ksem_wait_args *uap)
  684 {
  685 
  686         return (kern_sem_wait(td, uap->id, 0, NULL));
  687 }
  688 
  689 #ifndef _SYS_SYSPROTO_H_
  690 struct ksem_timedwait_args {
  691         semid_t         id;
  692         const struct timespec *abstime;
  693 };
  694 #endif
  695 int
  696 ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap)
  697 {
  698         struct timespec abstime;
  699         struct timespec *ts;
  700         int error;
  701 
  702         /*
  703          * We allow a null timespec (wait forever).
  704          */
  705         if (uap->abstime == NULL)
  706                 ts = NULL;
  707         else {
  708                 error = copyin(uap->abstime, &abstime, sizeof(abstime));
  709                 if (error != 0)
  710                         return (error);
  711                 if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
  712                         return (EINVAL);
  713                 ts = &abstime;
  714         }
  715         return (kern_sem_wait(td, uap->id, 0, ts));
  716 }
  717 
  718 #ifndef _SYS_SYSPROTO_H_
  719 struct ksem_trywait_args {
  720         semid_t         id;
  721 };
  722 #endif
  723 int
  724 ksem_trywait(struct thread *td, struct ksem_trywait_args *uap)
  725 {
  726 
  727         return (kern_sem_wait(td, uap->id, 1, NULL));
  728 }
  729 
  730 static int
  731 kern_sem_wait(struct thread *td, semid_t id, int tryflag,
  732     struct timespec *abstime)
  733 {
  734         struct timespec ts1, ts2;
  735         struct timeval tv;
  736         struct file *fp;
  737         struct ksem *ks;
  738         int error;
  739 
  740         DP((">>> kern_sem_wait entered! pid=%d\n", (int)td->td_proc->p_pid));
  741         error = ksem_get(td, id, &fp);
  742         if (error)
  743                 return (error);
  744         ks = fp->f_data;
  745         mtx_lock(&sem_lock);
  746         DP((">>> kern_sem_wait critical section entered! pid=%d\n",
  747             (int)td->td_proc->p_pid));
  748 #ifdef MAC
  749         error = mac_posixsem_check_wait(td->td_ucred, fp->f_cred, ks);
  750         if (error) {
  751                 DP(("kern_sem_wait mac failed\n"));
  752                 goto err;
  753         }
  754 #endif
  755         DP(("kern_sem_wait value = %d, tryflag %d\n", ks->ks_value, tryflag));
  756         vfs_timestamp(&ks->ks_atime);
  757         while (ks->ks_value == 0) {
  758                 ks->ks_waiters++;
  759                 if (tryflag != 0)
  760                         error = EAGAIN;
  761                 else if (abstime == NULL)
  762                         error = cv_wait_sig(&ks->ks_cv, &sem_lock);
  763                 else {
  764                         for (;;) {
  765                                 ts1 = *abstime;
  766                                 getnanotime(&ts2);
  767                                 timespecsub(&ts1, &ts2);
  768                                 TIMESPEC_TO_TIMEVAL(&tv, &ts1);
  769                                 if (tv.tv_sec < 0) {
  770                                         error = ETIMEDOUT;
  771                                         break;
  772                                 }
  773                                 error = cv_timedwait_sig(&ks->ks_cv,
  774                                     &sem_lock, tvtohz(&tv));
  775                                 if (error != EWOULDBLOCK)
  776                                         break;
  777                         }
  778                 }
  779                 ks->ks_waiters--;
  780                 if (error)
  781                         goto err;
  782         }
  783         ks->ks_value--;
  784         DP(("kern_sem_wait value post-decrement = %d\n", ks->ks_value));
  785         error = 0;
  786 err:
  787         mtx_unlock(&sem_lock);
  788         fdrop(fp, td);
  789         DP(("<<< kern_sem_wait leaving, pid=%d, error = %d\n",
  790             (int)td->td_proc->p_pid, error));
  791         return (error);
  792 }
  793 
  794 #ifndef _SYS_SYSPROTO_H_
  795 struct ksem_getvalue_args {
  796         semid_t         id;
  797         int             *val;
  798 };
  799 #endif
  800 int
  801 ksem_getvalue(struct thread *td, struct ksem_getvalue_args *uap)
  802 {
  803         struct file *fp;
  804         struct ksem *ks;
  805         int error, val;
  806 
  807         error = ksem_get(td, uap->id, &fp);
  808         if (error)
  809                 return (error);
  810         ks = fp->f_data;
  811 
  812         mtx_lock(&sem_lock);
  813 #ifdef MAC
  814         error = mac_posixsem_check_getvalue(td->td_ucred, fp->f_cred, ks);
  815         if (error) {
  816                 mtx_unlock(&sem_lock);
  817                 fdrop(fp, td);
  818                 return (error);
  819         }
  820 #endif
  821         val = ks->ks_value;
  822         vfs_timestamp(&ks->ks_atime);
  823         mtx_unlock(&sem_lock);
  824         fdrop(fp, td);
  825         error = copyout(&val, uap->val, sizeof(val));
  826         return (error);
  827 }
  828 
  829 #ifndef _SYS_SYSPROTO_H_
  830 struct ksem_destroy_args {
  831         semid_t         id;
  832 };
  833 #endif
  834 int
  835 ksem_destroy(struct thread *td, struct ksem_destroy_args *uap)
  836 {
  837         struct file *fp;
  838         struct ksem *ks;
  839         int error;
  840 
  841         error = ksem_get(td, uap->id, &fp);
  842         if (error)
  843                 return (error);
  844         ks = fp->f_data;
  845         if (!(ks->ks_flags & KS_ANONYMOUS)) {
  846                 fdrop(fp, td);
  847                 return (EINVAL);
  848         }
  849         mtx_lock(&sem_lock);
  850         if (ks->ks_waiters != 0) {
  851                 mtx_unlock(&sem_lock);
  852                 error = EBUSY;
  853                 goto err;
  854         }
  855         ks->ks_flags |= KS_DEAD;
  856         mtx_unlock(&sem_lock);
  857 
  858         error = kern_close(td, uap->id);
  859 err:
  860         fdrop(fp, td);
  861         return (error);
  862 }
  863 
  864 static struct syscall_helper_data ksem_syscalls[] = {
  865         SYSCALL_INIT_HELPER(ksem_init),
  866         SYSCALL_INIT_HELPER(ksem_open),
  867         SYSCALL_INIT_HELPER(ksem_unlink),
  868         SYSCALL_INIT_HELPER(ksem_close),
  869         SYSCALL_INIT_HELPER(ksem_post),
  870         SYSCALL_INIT_HELPER(ksem_wait),
  871         SYSCALL_INIT_HELPER(ksem_timedwait),
  872         SYSCALL_INIT_HELPER(ksem_trywait),
  873         SYSCALL_INIT_HELPER(ksem_getvalue),
  874         SYSCALL_INIT_HELPER(ksem_destroy),
  875         SYSCALL_INIT_LAST
  876 };
  877 
  878 #ifdef COMPAT_FREEBSD32
  879 #include <compat/freebsd32/freebsd32.h>
  880 #include <compat/freebsd32/freebsd32_proto.h>
  881 #include <compat/freebsd32/freebsd32_signal.h>
  882 #include <compat/freebsd32/freebsd32_syscall.h>
  883 #include <compat/freebsd32/freebsd32_util.h>
  884 
  885 int
  886 freebsd32_ksem_init(struct thread *td, struct freebsd32_ksem_init_args *uap)
  887 {
  888 
  889         return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
  890             0, 1));
  891 }
  892 
  893 int
  894 freebsd32_ksem_open(struct thread *td, struct freebsd32_ksem_open_args *uap)
  895 {
  896 
  897         if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
  898                 return (EINVAL);
  899         return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
  900             uap->oflag, 1));
  901 }
  902 
  903 int
  904 freebsd32_ksem_timedwait(struct thread *td,
  905     struct freebsd32_ksem_timedwait_args *uap)
  906 {
  907         struct timespec32 abstime32;
  908         struct timespec *ts, abstime;
  909         int error;
  910 
  911         /*
  912          * We allow a null timespec (wait forever).
  913          */
  914         if (uap->abstime == NULL)
  915                 ts = NULL;
  916         else {
  917                 error = copyin(uap->abstime, &abstime32, sizeof(abstime32));
  918                 if (error != 0)
  919                         return (error);
  920                 CP(abstime32, abstime, tv_sec);
  921                 CP(abstime32, abstime, tv_nsec);
  922                 if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
  923                         return (EINVAL);
  924                 ts = &abstime;
  925         }
  926         return (kern_sem_wait(td, uap->id, 0, ts));
  927 }
  928 
  929 static struct syscall_helper_data ksem32_syscalls[] = {
  930         SYSCALL32_INIT_HELPER(freebsd32_ksem_init),
  931         SYSCALL32_INIT_HELPER(freebsd32_ksem_open),
  932         SYSCALL32_INIT_HELPER(ksem_unlink),
  933         SYSCALL32_INIT_HELPER(ksem_close),
  934         SYSCALL32_INIT_HELPER(ksem_post),
  935         SYSCALL32_INIT_HELPER(ksem_wait),
  936         SYSCALL32_INIT_HELPER(freebsd32_ksem_timedwait),
  937         SYSCALL32_INIT_HELPER(ksem_trywait),
  938         SYSCALL32_INIT_HELPER(ksem_getvalue),
  939         SYSCALL32_INIT_HELPER(ksem_destroy),
  940         SYSCALL_INIT_LAST
  941 };
  942 #endif
  943 
  944 static int
  945 ksem_module_init(void)
  946 {
  947         int error;
  948 
  949         mtx_init(&sem_lock, "sem", NULL, MTX_DEF);
  950         mtx_init(&ksem_count_lock, "ksem count", NULL, MTX_DEF);
  951         sx_init(&ksem_dict_lock, "ksem dictionary");
  952         ksem_dictionary = hashinit(1024, M_KSEM, &ksem_hash);
  953         p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 200112L);
  954         p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
  955         p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
  956 
  957         error = syscall_helper_register(ksem_syscalls);
  958         if (error)
  959                 return (error);
  960 #ifdef COMPAT_FREEBSD32
  961         error = syscall32_helper_register(ksem32_syscalls);
  962         if (error)
  963                 return (error);
  964 #endif
  965         return (0);
  966 }
  967 
  968 static void
  969 ksem_module_destroy(void)
  970 {
  971 
  972 #ifdef COMPAT_FREEBSD32
  973         syscall32_helper_unregister(ksem32_syscalls);
  974 #endif
  975         syscall_helper_unregister(ksem_syscalls);
  976 
  977         p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 0);
  978         hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
  979         sx_destroy(&ksem_dict_lock);
  980         mtx_destroy(&ksem_count_lock);
  981         mtx_destroy(&sem_lock);
  982         p31b_unsetcfg(CTL_P1003_1B_SEM_VALUE_MAX);
  983         p31b_unsetcfg(CTL_P1003_1B_SEM_NSEMS_MAX);
  984 }
  985 
  986 static int
  987 sem_modload(struct module *module, int cmd, void *arg)
  988 {
  989         int error = 0;
  990 
  991         switch (cmd) {
  992         case MOD_LOAD:
  993                 error = ksem_module_init();
  994                 if (error)
  995                         ksem_module_destroy();
  996                 break;
  997 
  998         case MOD_UNLOAD:
  999                 mtx_lock(&ksem_count_lock);
 1000                 if (nsems != 0) {
 1001                         error = EOPNOTSUPP;
 1002                         mtx_unlock(&ksem_count_lock);
 1003                         break;
 1004                 }
 1005                 ksem_dead = 1;
 1006                 mtx_unlock(&ksem_count_lock);
 1007                 ksem_module_destroy();
 1008                 break;
 1009 
 1010         case MOD_SHUTDOWN:
 1011                 break;
 1012         default:
 1013                 error = EINVAL;
 1014                 break;
 1015         }
 1016         return (error);
 1017 }
 1018 
 1019 static moduledata_t sem_mod = {
 1020         "sem",
 1021         &sem_modload,
 1022         NULL
 1023 };
 1024 
 1025 DECLARE_MODULE(sem, sem_mod, SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
 1026 MODULE_VERSION(sem, 1);

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